White Bean Puree
1 cup chicken stock
1 tbsp. olive oil
2 small sprigs fresh rosemary
1 large clove garlic, crushed
1 can (about 15 oz.) white beans, drained
½ lemon, juiced (about 2 tbsp.)
4 branzino fillets (6 to 8 oz. each)
Salt and pepper
1 tbsp. refined olive oil (light in flavor and color), or 1 tbsp. canola or vegetable oil
4 tbsp. butter, cut in pieces
¼ cup capers, drained and patted dry
¼ cup dry (white) vermouth or white wine
1 lemon, juiced (about 1/4 cup)
In a small saucepan or pot, bring the stock, olive oil, rosemary sprigs, and garlic to a boil. Cook until reduced by half, about 5 minutes. Discard the rosemary stems, leaving any leaves behind in the pan. Add the beans and lemon juice. Cook until warm, about 2 minutes. Transfer to a blender or food processor and puree; season with salt. Leave the lid on the blender to keep warm.
Heat a large skillet over high. Season the fish all over with salt and pepper. Add the refined olive oil to the skillet, one turn of pan. When the oil shimmers, add the fish, skin-side down. Cook, pressing the fish with a spatula to keep the skin flat, until the skin is crisp, 2 to 3 minutes. Flip and cook until almost opaque in the center, about 1 minute more. Remove from heat. Let stand for 1 to 2 minutes.
In a small skillet, melt the butter over medium heat. Add the capers. Cook until browned, 7 to 8 minutes. Whisk in the vermouth and lemon juice. Cook until the sauce is reduced slightly, 1 to 2 minutes.
Divide the bean puree among 4 plates. Top with the fish, skin-side up, then the sauce.